Device for cutting a vertical slot-like unloading opening

ABSTRACT

A device is provided for creating vertical slot-like unloading openings approximate to a well, comprising: a casing pipe enclosed into the well, a generator of abrasive hydro-jets, a column for delivering the hydro-jets, a hydraulic brake, a perforator descended into the casing pipe including a pair of nozzles for creating the hydro-jets, a pair of centralisers mounted on the perforator, and a pair of cutting rotating discs, mounted under the pair of nozzles on racks, partially springly retractable and projectable depending on hydro-jet pressure. Additional embodiments include: designing turnable racks, mounting the centralisers on similar projectable and retractable racks, installing an additional pair of centralisers, selecting their installation places, setting predetermined ranges of the racks projection and retraction in static and perforation modes. The innovations allow for accelerated cutting of the casing pipe, improving accuracy of the openings, and increasing durability and reliability of the device.

TECHNICAL FIELD

The invention relates to mining, oil and gas extracting, hydro-geological, engineering-geological and water supply industries, and specifically to cutting vertical slot-like openings in near-well zones approximate to productive formation layers by means of an abrasive hydro-jet.

BACKGROUND OF THE INVENTION

Oil, gas, injection, hydro-geological and water supply wells are in great demand all over the world; a huge number of specialists improve them constantly, increase their effectiveness and lifespan, make them less expensive, etc.

It is known that one of the most effective ways for increasing the productivity of oil, gas, supercharging, hydro-geological, engineering-geological, or water supply wells is a slot unloading opening made in the near-well zone of underground productive formation layers.

The proposed method provides for creation of slots in the near-well zone, wherein the width, depth and orientation of slots being predetermined by known methods from characteristics of the well and the productive layers such as, for instance, described in U.S. Pat. Nos. 3,966,992, 5,337,825, 6,651,741, 7,073,587, in a U.S. patent application Ser. No. 10/957,871, in an international application PCT/RU93/00101, USSR inventor's certificate No 1031263, and a Russian Federation patent RU2074957.

Cutting the slot openings with preset parameters is a complicated engineering problem, because the cutting is performed under conditions of different rocks, temperatures, at great depths, in the presence of products to be extracted, and rinsing liquids in the well, while it can be controlled and monitored only remotely.

One of the most successful methods for cutting the slot-like openings is a hydro-abrasive perforation wherein the cutting is performed by a jet of liquid with sand at high pressure. The device for implementation of aforesaid method is the closest prior art with regard to its technical substance and disclosed in U.S. Pat. No. 6,651,741 issued on Nov. 25, 2003. This device is illustrated in a general form in FIG. 1 of the present disclosure.

The device includes a generator of abrasive sand-hydro-jet (1), connected via a column of pump-compressor pipes (2) (also called a PCP column) to a perforator (3). The perforator is lowered into the well inside a casing pipe (4) arranged inside a well (6). The column 2 is composed of pump-compressor pipes sequentially connected in a series. The perforator 3 includes an interior cavity, two diametrically placed nozzles (5), directed at the wall of the well, and a ball valve (7) mounted at the end of the perforator. Centralisers (13) are mounted on the perforator body; the longitudinal axes of the centralisers are oriented perpendicularly to the longitudinal axes of nozzles 5 and symmetrically to each other. The column 2 is connected to the perforator 3 via a hydraulic brake (8) enclosed in a tubular hull and having a cocking mechanism and a return mechanism. The hydraulic brake 8 includes an internal tube and an external tube, an upper chamber and a lower chamber communicating through a cross-flow channel.

A surface part of the prior art device (surface equipment) includes standard means available at oil-rigs and lifting assemblies for well repair: a displacement device (9) for controlled unloading and displacing the PCP column 2; a weight meter (10) of the column 2; a preventor (11) that is a means for providing a hermetic sealing at the top of the well 6, and an abrasive jet pressure meter (12).

The upper chamber of hydraulic brake 8 is filled with a viscous operating liquid at a laboratory-workshop. The liquid properties are selected for each type of cutting in accordance with preset conditions for the device operation in the well (temperature, pressure, physical-mechanical properties of the casing pipe 4 and the rocks forming the productive formation layer), which conditions are simulated in the laboratory-workshop. The device is adjusted by selecting certain parameters. These parameters are: fluidity of the viscous liquid, diameter and length of the cross-flow channel, temperature and pressure anticipated during the device operation, as well as expected changes of the parameters caused by the temperature, pressure, efficiency of the abrasive hydro-jet.

The device shown in FIG. 1 operates as follows. The tubular hull of the hydraulic brake 8 is connected by a muff (not shown) to a first end of the column 2; a second end of the column 2 is connected to the generator of the abrasive hydro-jet 1 of the surface equipment.

Then the column 2 (along with the hydraulic brake 8 with the cocking mechanism, the perforator 3 with the ball valve 7) is lowered into the casing pipe 4 of the well 6 down at a preset depth so that the nozzles 5 of the perforator 3 would be at the well point corresponding to the upper edge (roof) of a vertical slot-like opening to be cut. Thereafter, a ball is thrown into the internal tube of the hydraulic brake through the column 2 to close the ball valve 7. The generator of abrasive hydro-jet 1 of the surface equipment is switched on and it starts injecting abrasive mixture into the internal tube of the device at a preset (pre-calculated) pressure. The mixture fills the internal tube up to the ball valve 7 and closes it tightly. Through the nozzles 5 the perforator 3 begins cutting the slots: at first—on the walls of the casing pipe 4 of the well 6, and then—in the near-well zone. The cutting depth of the future slot-like opening depends, in particular, on the speed of the perforator's movement along the casing pipe 4. The centralisers 13 ensure the positioning of the perforator 3 in the centre of the casing pipe 4 by repelling from the internal walls of the pipe 4.

It should be noted that it is technologically impossible to perform operative control of the speed of the perforator's movement during the cutting process. To get information about the end of the working stroke of the hydraulic brake some special signal devices are used. Such a device may be implemented, for example, in the form of an upward pin mounted under the ball valve 7. At the end of the working stroke of the hydraulic brake this pin will open the ball valve 7 (i.e. it will eject the ball out of the ball valve 7). As a result, the pressure will decrease sharply in the pipe space (due to opening of the pipe at the bottom of the perforator's 3 body), which is the reliable information about the end of the working stroke. The prior art device and its operation are described in more detail in the aforementioned references.

Analysis of the processes taking place during the cutting of slots by the abrasive hydro-jet method follows. The perforator 3 is lowered into the well 6 being attached to the column 2. During its operation, the perforator is moved along the casing pipe 4 at a speed determined by the preset parameters of the hydraulic brake 8.

The speed of the perforator's movement is selected by the operator beforehand according to a calculated speed of cutting the slot-like opening by the abrasive hydro-jet. As mentioned above, the perforator's movement speed (determined by the time for cutting the casing pipe portion and the well's wall portion) is preset according to the selection of the operating liquid composition in the hydraulic brake and the cross-section area of the cross-flow channels. It is known that the greater part of cutting time (typically more than 90%) is allocated to cutting the casing pipe 4, while typically less than 10% is allocated to cutting a rock of the well's wall, since the strength of the casing pipe 4 is usually much higher than that of the rock. Due to inevitable processing deviations in the thickness and material of the casing pipe 4, the time for its cutting will be different throughout its height. As a result, the time remaining for cutting the rock will also vary and in percentage terms. Such variations can be several times more than the variations for cutting the pipe 4. Therefore, the depth of the slot actually cut will essentially differ from the calculated (preset) one.

Since it is impossible to control the size of an actually cut slot opening during its perforation (“creation”), the perforator will be lowered at a certain preset speed, regardless of the depth of the opening actually cut and the quality of perforation of the casing pipe (the pipe is often turned out to be perforated “in a dashed manner”). The operator will be only able to state the moment of the pressure change of the sand hydro-jet pump associated with the end of the working stroke of the hydraulic brake. At this moment, the pressure will sharply decrease in the PCP pipe due to an abrupt increase of the cross-section area of the outgoing jet holes.

The result of cutting (slot's depth) can be evaluated only upon the completion of cutting the slot opening by complicated measurements utilizing special expensive equipment and technologies (for example, acoustic scanning of the near-well zone). In practice, it is not a rare case, when at a certain descent speed of the perforator, the sand hydro-jet doesn't have sufficient time to cut the casing pipe's wall, and in this case no slot will be formed at all at this point of the well's wall.

Moreover, the centralisers 13, designed for positioning the perforator in the centre of the casing pipe, not always fulfil this function. Usually, they are represented by streamlined caps or rectangular plates of substantially equal height, mounted around the circumference of the perforator body being oriented perpendicularly to each other and to the vertical (longitudinal) axis of the perforator. The height of centralisers is so selected that they would move out at a predetermined projecting distance within the range of from 3 mm to 5 mm over the end of the abrasive hydro-jet nozzle, and the outside diameter of the centralisers would fit into the casing pipe to be treated. If, during the descent of the pump-compressor pipe 2, the perforator is deviated from the centre by more than the predetermined projecting distance, the centralisers will repel the pump-compressor pipe 2 along with the perforator from the wall of the casing pipe 4. In this case, during its descent, the perforator will not be situated exactly at the centre of the casing pipe, but will deviate within the projecting distance from the centre.

This circumstance results in the fact that the perforator forms asymmetric cuts on the walls of the well. The cuts may be much larger on one side than on the other side, and even to the extent that the perforation would not reach the rock on one of the sides at all. It can be noticed that one cannot decrease the projecting distance by increasing correspondingly the height of pins and their strength, because they would hitch against the walls of the pipe 2 and hinder its free descent.

Yet another peculiarity of using the described centralisers should be noted. Since they do not stabilize radial and azimuthal positions of the perforator with respect to the walls of the well, the performed slot opening is turned out to be not strictly vertical, but it fluctuates about the vertical. As a result, the width of the opening is greater than the pre-calculated one; the energy of the abrasive hydro-jet is wasted to cut a wider opening at the expense of its depth. In terms of quality of the unloading slot opening and the well productivity, these are reject and real loss. The described devices are widespread in modern practice, i.e. the industry losses are significant.

Thusly, the above analysis shows that those prior art devices have the following shortcomings: (a) The speed of cutting slot-like openings is low because it is mainly determined by the speed of cutting the casing pipes. (b) The depth of cutting the rock with preset parameters of the hydraulic brake is not constant and may differ considerably from the pre-calculated one. This is due to the fact that the depth of the slot opening is not controlled during the cutting process. The perforator 3 is lowered according to preset adjustments of the hydraulic brake 8. (c) In addition to the above-mentioned causes, the actual depth of the slot opening may differ considerably from the pre-calculated one because of jet pressure fluctuations, abrasive composition, deviations in thickness and strength of the casing pipe 4 and rock characteristics. (d) Also, the fact that the perforator position may deviate from the centre of the casing pipe, as well as the fact that the azimuthal position of the perforator with respect to the pipe is not fixed, significantly affect the quality of the resultant slot.

Therefore, a real need exists for increasing the productivity of devices for cutting slot-like openings, for improving the accuracy of cutting and implementing an operative control of the cutting process.

OBJECT AND BRIEF DESCRIPTION OF THE INVENTION

An aim of the invention is to increase the speed and accuracy of cutting slot-like openings and provide an operative control of the cutting process. Other aims of the invention will become apparent from a consideration of the drawings, ensuing description, and claims as hereinafter related.

The aforesaid aim is achieved as follows below. A known device for cutting a vertical unloading slot-like opening in a well typically comprises a generator of abrasive hydro-jet, connected by a column of pump-compressor pipes (PCP column) via a hydraulic brake, having a return mechanism, to a perforator, descended into a casing pipe disposed inside of the well. The perforator includes two diametrically placed nozzles, directed to the well wall, and centralisers. According to the invention, substantially new features, alterations, and additions have been introduced to the device.

For acceleration of the slot cutting, a pair of cutting rotating discs is introduced, which discs are made partially retractable by a spring into the perforator body and capable of being automatically drawn out in a casing pipe perforation mode under pressure developed in the PCP column. The aforesaid pair of cutting discs is mounted under the pair of perforator nozzles, the planes of the cutting discs being oriented vertically and perpendicularly towards the well's wall along the directions of the abrasive hydro-jets.

To provide the mentioned partial retraction of the cutting discs into the perforator body in a static mode and their automatic projecting in the casing pipe perforation mode, the cutting discs are mounted on movable racks. The racks are connected by means of pull-in springs to the perforator body and via expulsive hydraulic channels to the perforator's interior cavity, whereas the expulsive force of the hydraulic channels ejecting the racks in the casing pipe perforation mode being greater than the traction force of the pull-in springs. Optionally, the racks may be designed turnable.

For optimising the device operation it is recommended that the cutting edge of discs, in the static mode, be projected out of the perforator body at a distance not greater than the difference between the inner radius of the casing pipe and the outer radius of the perforator, and, in the casing pipe perforation mode, at a distance equal to at least the difference between the inner radius of the casing pipe and the outer radius of the perforator.

To enhance the quality and accuracy of cutting a slot opening, the pair of centralisers may be placed at the level of location of the perforator's nozzles or at a location not exceeding the range of from 3 to 5 cm above this level. The axis extending through the pair of centralisers is oriented perpendicular to the axis extending through the pair of nozzles.

For further enhancement of the quality and accuracy of cutting a slot opening, at least one additional pair of centralisers may be introduced to be located beneath the perforator's nozzles in parallel to the first pair of centralisers.

To increase the device reliability (to decrease breakage of centralisers) the centralisers may be mounted on racks, which are connected by means of pull-in springs to the perforator body and via expulsive hydraulic channels to the perforator's interior space. The expulsive pressure force of the hydraulic channel should be greater than the traction force of the pull-in springs.

In an optional embodiment, the racks of centralisers may be designed turnable. Of course, for manufacturing the cutting edges of the cutting discs, one should select a material whose strength would be greater than that of the material the casing pipe is made of, so that to enable the discs to cut the casing pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic sectional view of a prior art device's structure.

FIG. 2 illustrates a schematic sectional view of the claimed device's structure, according to an embodiment of the present invention.

FIG. 3 illustrates a schematic sectional view of the perforator with a cutting disc on a retractable rack, according to an embodiment of the present invention.

FIG. 4 illustrates a schematic sectional view of the perforator with a cutting disc on a turnable rack, according to an embodiment of the present invention.

The following reference numerals are used to mean the following units and structural members: 1—generator of abrasive hydro-jet, 2—column of pump-compressor pipes (PCP column), 3—perforator, 4—casing pipe, 5—nozzles, 6—well, 7—ball valve, 8—hydraulic brake with cocking and return devices, 9—device for controlled unloading and displacing the PCP column, 10—weight meter (dynamometer), 11—preventer, 12—abrasive hydro-jet pressure meter (manometer), 13—centraliser, 14—cutting disc, 15—retractable rack of the cutting disc, 16—pull-in spring of the rack, 17—hydraulic channel ejecting the rack, 18—turnable rack of the cutting disc, 19—centraliser rack.

DETAIL DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

While the invention may be susceptible to embodiment in different forms, there are shown in the drawings and will be described in detail herein specific embodiments of the present invention, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein.

A preferred embodiment of the inventive device for making a slot opening in a substantially vertical well 6, illustrated in FIG. 2, comprises a casing pipe 4 (or a column composed of sequentially assembled pipes) enclosed into the well 6; a generator of abrasive hydro-jet 1 mounted on the ground surface in proximity of the well 6; a PCP column 2 for conducting the hydro-jet liquid, the column 2 is composed of sequentially assembled pump-compressor pipes, a first (upper) end of the column 2 is connected to the generator 1, the column 2 is enclosed into the casing pipe 4; a hydraulic brake 8 including a tubular hull connected by a muff (not shown) to a second (lower) end of the column 2, the hydraulic brake 8 includes an internal tube and an external tube (not shown), an upper chamber and a lower chamber communicating through a cross-flow channel (not shown), the hydraulic brake 8 includes a cocking device and a return device (not shown); a perforator 3, connected with the hydraulic brake 8, the perforator 3 is lowered into the well 6 inside the casing pipe 4, the perforator 3 includes two diametrically placed nozzles 5 (other embodiment may include more than two nozzles), mounted thereon, and oppositely directed towards the wall of the well 6, the perforator 3 includes a ball valve 7 mounted at the end of the perforator 3, the perforator 3 includes centralisers 13 and a pair of rotatable cutting discs 14 mounted on its body (other embodiments may include more than two cutting discs); a device 9 for controlled unloading and displacing the PCP column 2, the device 9 is mounted at the ground surface in proximity of the top of well 6 and associated with the column 2; a PCP column weight meter 10 associated with the column 2; a device 11 for sealing the top opening of the well 4, and a jet pressure meter 12 associated with the generator of abrasive hydro-jet 1.

FIG. 3 shows in detail the installation of the centralisers 13 and the cutting discs 14 in the perforator body. The cutting discs 14 are mounted on retractable racks 15. The racks 15 are connected by means of a pull-in spring 16 to the perforator body 3 and via an expulsive hydraulic channel 17 to the perforator's interior cavity. The installation of the centralisers 13 in this example is performed in a way similar to the previously described: the streamlined caps of centralisers 13 are mounted on the racks 19, connected by means of the pull-in springs 16 to the perforator body 3 and via the expulsive hydraulic channels 17 to the interior cavity of the perforator 3. In other words, the hydraulic channels 17 are connected to the racks 15 and 19 of cutting discs 14 and centralisers 13 respectively.

The spring 16 has a first spring end attached to the perforator body, and a second spring end. Each rack is attached to the second spring end and is attracted with a predetermined traction force tending to retract the rack. On the other hand, the rack is connected to the hydraulic channels and is repelled with the expulsive force, developed due to a pressure of the hydro-jet in the perforator's interior cavity.

FIG. 4 provides a detailed illustration of the installation of the cutting disc 14 in the perforator body on the turnable rack 18.

In a casing pipe perforation mode, the expulsive force tends to eject the rack during operation of the perforator, wherein the expulsive force should be greater than the traction force. Therefore, the expulsive force of hydraulic channels 17 in the perforation mode is greater than the traction force of the pull-in spring 16. In the perforation mode the cutting edge of disc 14 is projected at a distance equal to at least the difference between the inner radius of casing pipe 4 and the outer radius of perforator 3. In a preferred embodiment, in the casing pipe perforation mode the cutting edge of the discs 14 is moved out of the perforator body for a distance equal to at least the difference between the inner radius of the casing pipe and the outer radius of the perforator plus an additional distance within the range of from 3 mm to 5 mm.

In a stationary or static mode (in absence of an abrasive hydro-jet), there is no expulsive force in the hydraulic channels; the pressure in the channels is equal to zero. In the static mode, the cutting edge of disc 14 is projected out of the perforator body 3 at a distance not exceeding the difference between the inner radius of casing pipe 4 and the outer radius of perforator 3.

Example of Operation of a Preferred Inventive Embodiment

A preferred embodiment of the device for cutting slot-like openings operates as follows. At first, the device is prepared for cutting a predetermined slot opening. The nozzles 5 of the perforator are oppositely directed outward. The perforator 3 is then attached to the end of the PCP column 2 (i.e. to the lower pipe of the PCP column) via the hydraulic brake 8. Thereafter, the lower pipe of the PCP column 2 along with the equipment mounted on it is connected to the column 2.

Next, the PCP column 2 along with the equipment mounted on it is descended at the maximal predetermined depth, and the well 6 is equipped with the sealing device 11. As an example, if the cutting is to be performed at depths from 1000 to 101 m, the end of the PCP column 2 should be lowered so that the nozzles 5 of the perforator 3 would be at a 1000 m depth. The cutting discs 14 and the centralisers 13 do not hinder this descent because they are partially retracted by pull-in springs 16 into the perforator body 3 (since the expulsive pressure of hydraulic channels 17 in the stationary mode is equal to zero).

The cutting edges of the cutting discs 14 and the caps of the centralisers 13 are projected out of the perforator body 3 for a distance not greater than that between the outer body of the perforator 3 and the inner wall of the casing pipe 4. As a result, the PCP column 2 along with the equipment is held suspended from the above (from the surface), using the device 9 for controlled unloading of the PCP column 2. After that, a ball is thrown into the column 2 to close the ball valve 7. The ball falls into a hole of the ball valve 7. The generator 1 of the abrasive hydro-jet is turned on and injects the abrasive solution under pressure into the column 2. The ball valve 7 closes tightly the hole under the pressure of abrasive solution. The hydraulic pressure in the perforator 3 increases sharply. At the same time, several important events take place.

Firstly, the expulsive pressure of hydraulic channels 17 moves both the discs 14 and the centralisers 13 outside of the perforator 3. The cutting discs 14 are depressed against the walls of the casing pipe 4, cut into the walls, and punch the pipe 4. The weight of the pump-compressor column 2 is about several tons, so that even when the cutting discs 14 are strongly depressed against the pipe 4, the column 2 can be descended following the operation of the hydraulic brake 8, i.e. creating a downward tangential punching pressure applied to the discs 14. This punching significantly accelerates the process of cutting a wall of the pipe 4. Moreover, the cutting discs 14 clearly fix the radial position of the perforator 3 relative to the casing pipe 4, substantially excluding the creation of uneven or dissimilar openings at the same level.

Secondly,—the caps of centralisers 13 will move out of the perforator body 3 and abut against the walls of the casing pipe 4, by centering the perforator's position.

Thirdly, a “washing-out” (cutting) the unloading slot opening will start through the nozzles 5 of the perforator 3. At first, the cutting discs 14 cut into the casing pipe 4, and then the abrasive hydro-jet 1 “washes” out the near-bottom zone.

When the cutting discs 14 punch the casing pipe 4 and are moved due to the reaction from a non-destructed part of the pipe, the weight of PCP column, measured by the device 10, will decrease by the value of a tangential force necessary for displacement of the cutting discs. As the hydraulic brake reaches the end of its working stroke, the opposite load on the cutting discs 14 will lessen to zero, and the device 10 measuring the weight of PCP column will show the initial (full) weight of the column 2.

In combination with the perforation of the casing pipe 4 by the cutting discs 14, the abrasive hydro-jet nozzles 5 operate by washing out an unloading slot in the near-well zone. At a force of about 2 tons pressed on the discs 14, the speed of perforation of the casing pipe 4 with a 6-mm wall will be about 40-50 mm/min. In parallel, the washing-out of the unloading slot takes place in the near-well zone. However, the perforator 3 is moved not at a natural speed of the casing pipe destruction but at a speed preset by the hydraulic brake 8. The displacement speed of the perforator is selected according to the speed of unloading of the slot's washing-out and is usually 20-25 mm/min, i.e. 4-5 times faster than the operation of the prior art device. At the end of the hydraulic brake's working stroke, the device 10, measuring the weight of PCP column, will show the initial (full) weight of the PCP column 2. The unloading slot in the near-well zone will be washed-out until the moment when the operating pressure of the abrasive hydro-jet decreases by 20-50 atmospheres as compared to the initial one. This fact indicates that the velocity of abrasive particles in the jet has lost the ability to destruct the rock, because the jet energy is decreased due to the drop in its velocity.

An important factor is that for the washing-out (cutting) an unloading slot in the near-well zone the amount of abrasive substance in the hydro-abrasive liquid can be reduced 2-3 times as compared to the abrasive hydro-jet used for perforation of a casing pipe allowing an increase of the abrasive wear resistance of the equipment and its term of use by a factor of 2-3.

From the aforesaid, it follows that a cutting-abrasive perforator during one descent into the well can treat productive strata, which are 10-20 times thicker than that of the prior art devices.

Since the perforator can be moved strictly along the generatrix of the casing pipe cylinder only after its perforation, and the full travel of the perforator is clearly and unambiguously indicated by the control device of PCP weight 10 (a “loss” of weight occurs only during the operation of the cutting discs when the hydraulic brake operates; when it reaches the end of its travel, the PCP “takes on” the full weight because the tangential reaction exerted from the casing pipe onto the perforator disappears), the operating person can be informed of the results of the cutting-abrasive operation. A sharp change in the column's weight is the reliable information about the end of the working stroke.

The depth of washing-out an unloading slot in the near-well zone is controlled by the value of pressure of the abrasive hydro-jet (the higher is the pressure, the higher is the cutting speed, the greater is the energy of an abrasive particle supplied by the jet), while physical-mechanical properties of the rocks forming the productive strata layers, within which an unloading slot is being washed-out in the near-well zone, allow to characterize with a high degree of confidence the size of the created unloading slot.

The given example of embodiment showed that the speed of cutting a slot opening has increased, its quality and reliability have enhanced.

NOVEL FEATURES OF THE INVENTION AND INDUSTRIAL APPLICABILITY

The novel features of the device are following: (a) introduction of cutting discs, selection of the place of their installation, development of their automatically projected design, selection of the projecting range of the discs in different modes; (b) introduction of newly designed automatically projected centralisers, selection of their installation place, selection of the projection range of the centralisers in different modes; (c) introduction of a second pair of centralisers and selection of the place of their installation; (d) selection of materials for the cutting edge of the discs. These innovations allow obtaining the effect of accelerated cutting of the casing pipe, improving accuracy of the slot opening sizes, and increasing durability and reliability of the device.

The proposed technical solutions have been reduced to practice. The devices have been experimentally manufactured. All elements, materials, technologies necessary for manufacturing the devices have been well mastered. The cost of the claimed devices is expected to be slightly higher than that of the prior art devices, however their productivity and the quality of unloading slot openings carried out with the inventive devices are expected to be significantly improved. This is evident from the above analysis, as well from data obtained during experiments.

The claimed devices were experimentally used to accelerate the creation of slot-like unloading openings in the near-well zone of producing formation. The devices did essentially increase the speed and the quality of operations. The tests confirmed the operational capability of the proposed device and the attaining of the invention goals set forth. During the test, four production formations were treated with the proposed device in different wells at depths of 6260-8590 ft with average thickness in the range of from 16 to 28 ft. In each case, an unloading slot opening was created for the entire thickness of production formation layer. In all cases, the speed of creation of the slot opening was by 380% higher than the calculated speed with the use of the prior art device.

The increase of the opening creation speed can be explained by the decrease of the cutting time of the casing pipe owing to a preliminary punching of the cut places by the cutting discs, as well as due to a stable and symmetrical position of the perforator relative to the casing pipe.

Another special experiment was carried out for the quantitative assessment of an increase in the speed of cutting the casing pipe. Two segments of the casing pipe were cut on the surface, cemented in a 1 m³ concrete block using a sand hydro-jet pump with capacity of 5-8 bbl/min at a pressure of 180-250 atmospheres, a hydro-abrasive perforator of the prior art device utilizing hydro-abrasive liquid (fresh water) with sand content of 50 g/l, and, on the other hand, a cutting-abrasive perforator (the claimed device) utilizing hydro-abrasive liquid (fresh water) with sand content of 15 g/l (i.e. the sand content was more than 3 times lower). The speed of cutting the casing pipe and creating the unloading slot opening was determined visually according to a washout in the concrete block. The difference in speed was over 300% in favour of the claimed device.

Since the prior art devices were used at the same sites before the use of the proposed inventive devices, it has been possible to compare their effectiveness directly. The average time of identical operations has decreased by nearly 300% (mainly, due to the acceleration in cutting the casing pipe), while the productivity of treated wells has increased by 350-700% (due to a more precise performance of the slots of necessary pre-calculated sizes in the near-well zone). Moreover, the reliability and durability of the device have enhanced considerably, due to a decrease in the number of centraliser breakages. 

1. A device for creating a vertical slot-like unloading opening in a zone approximate to a well, said device comprising: a casing pipe enclosed into the well; a generator of abrasive hydro-jet mounted in proximity to the well on the ground surface, said generator capable to develop a predetermined pressure of the hydro-jet; a column of pump-compressor pipes for conducting the hydro-jet, said column enclosed into the casing pipe, the upper end of said column connected to the generator; a hydraulic brake having a first end and a second end, with the first end substantially connected to the lower end of said column; a perforator capable to be descended into the casing pipe while being controlled by the hydraulic brake, said perforator connected to the second end of said hydraulic brake, said perforator having at least a body and an interior cavity therein, said perforator including at least one pair of nozzles for creation of abrasive hydro-jets, said nozzles diametrically mounted on said perforator body, the nozzles oriented at directions towards the well wall, at least one pair of centralisers mounted on said perforator body, and at least one pair of cutting rotating discs, partially springly retracted into the perforator body and capable of being automatically projected into the casing pipe depending on said pressure of the hydro-jet, said pair of cutting discs being mounted under the pair of nozzles, wherein the planes of said cutting discs oriented vertically and perpendicularly to the well wall corresponding to the directions of said nozzles.
 2. The device according to 1, wherein said device capable of operation in a static mode particularly characterized in that the cutting edge of said discs being moved out of the perforator body for a distance not exceeding the difference between the inner radius of the casing pipe and the outer radius of the perforator, and in a casing pipe perforation mode particularly characterized in that the cutting edge of said discs being moved out of the perforator body for a distance equal to at least the difference between the inner radius of the casing pipe and the outer radius of the perforator plus an additional distance within the range of from 3 mm to 5 mm.
 3. The device according to claim 1, further including: at least one pair of expulsive hydraulic channels connected to said interior cavity and capable to conduct the hydro-jet creating a predetermined expulsive force therein; at least one pair of pull-in springs, each said spring having a first spring end connected to the perforator body, and a second spring end; at least one pair of movable racks, said racks each connected to the second spring end of each said spring and being attracted with a predetermined traction force tending to retract the racks, said racks connected to said hydraulic channels and being repelled with the expulsive force tending to eject the racks; the cutting discs being fixedly mounted on said racks; and the expulsive force being greater than the traction force during operation of the perforator.
 4. The device according to 3, wherein said device capable of operation in a static mode characterized in that the cutting edge of said discs being moved out of the perforator body for a distance not exceeding the difference between the inner radius of the casing pipe and the outer radius of the perforator, and in a casing pipe perforation mode characterized in that the cutting edge of said discs being moved out of the perforator body for a distance equal to at least the difference between the inner radius of the casing pipe and the outer radius of the perforator plus an additional distance within the range of from 3 mm to 5 mm.
 5. The device according to claim 3, wherein said racks being turnable.
 6. The device according to claim 5, wherein said device capable of operation in a static mode characterized in that the cutting edge of said discs being moved out of the perforator body for a distance not exceeding the difference between the inner radius of the casing pipe and the outer radius of the perforator, and in a casing pipe perforation mode characterized in that the cutting edge of said discs being moved out of the perforator body for a distance equal to at least the difference between the inner radius of the casing pipe and the outer radius of the perforator plus an additional distance within the range of from 3 mm to 5 mm.
 7. The device according to claim 1, wherein the pair of said centralisers disposed substantially at the level of location of the pair of said nozzles and the axis connecting the centralisers being perpendicular to the axis connecting the nozzles.
 8. The device according to claim 1, wherein the pair of said centralisers disposed at the level within the range of from 3 cm to 5 cm above the level of location of the pair of said nozzles, and the axis connecting these centralisers being perpendicular to the axis connecting the nozzles.
 9. The device according to claim 1, wherein at least one additional pair of centralisers disposed beneath said nozzles in parallel to said pair of centralisers.
 10. The device according to claim 9, wherein the centralisers of said pair of centralisers and of said additional pair of centralisers being mounted on additional racks; said additional racks connected by means of additional pull-in springs to the perforator body; said additional pull-in springs capable to develop a predetermined additional traction force applied to the additional racks; said additional racks connected to additional expulsive hydraulic channels communicating with said interior space; said additional expulsive hydraulic channels capable to develop a predetermined additional expulsive force; and the additional expulsive force being greater than the additional traction force.
 11. The device according to claim 3, wherein at least one additional pair of centralisers disposed beneath said nozzles in parallel to said pair of centralisers.
 12. The device according to claim 11 wherein the centralisers of said pair of centralisers and of said additional pair of centralisers being mounted on additional racks; said additional racks connected by means of additional pull-in springs to the perforator body; said additional pull-in springs capable to develop a predetermined additional traction force applied to the additional racks; said additional racks connected to additional expulsive hydraulic channels communicating with said interior space; said additional expulsive hydraulic channels capable to develop a predetermined additional expulsive force; and the additional expulsive force being greater than the additional traction force.
 13. The device according to claim 1, further comprising at least one pair of expulsive hydraulic channels connected to said interior cavity and capable to conduct the hydro-jet creating a predetermined expulsive force therein; at least one pair of pull-in springs, each said spring having a first spring end connected to the perforator body, and a second spring end; at least one pair of movable racks, said racks each connected to the second spring end of each said spring and being attracted with a predetermined traction force tending to retract the racks, said racks connected to said hydraulic channels and being repelled with the expulsive force tending to eject the racks; said centralisers being fixedly mounted on said racks; and the expulsive force being greater than the traction force during operation of the perforator.
 14. The device according to claim 10, wherein said additional racks being turnable.
 15. The device according to claim 12, wherein said additional racks being turnable.
 16. The device according to claim 13, wherein said racks being turnable.
 17. The device according to claim 1, wherein the strength of the material of the cutting edges of said cutting discs being greater than that of the material of said casing pipe. 